The present invention relates to processing gemstones to enhance their color, and in particular, to color enhancement through gamma ray bombardment.
In the early 1970's, Joe Borden and Charles Key produced and marketed sky blue topaz stones which had been subjected to electron bombardment. The color of these stones varied from light blue through extremely intense shades which could not be distinguished in appearance from California Blue. They also produced and marketed a small number of topaz gemstones with extremely dark colors, even to the point of showing some greenish and greyish overtones. The color of the gemstones depended upon the source of rough topaz and the dose of radiation. Each stone was found to have a color saturation point beyond which further irradiation would not enhance the color or would not be cost effective in further enhancing the color. The size of such sky blue topaz stones that could be produced was severely limited by the ability of 8-17MEV electrons to penetrate more than approximately three-quarters of an inch of topaz, the ability of the topaz to dissipate heat at the rate of energy applied, and the size of container used to allow forced circulation of water for cooling the stones during irradiation.
Also in the early 1970's, Romanelle & Associates perfected the neutron irradiation of topaz gemstones in Britain to create "London Blue". These gemstones had a very dark color, which sometimes had a grey or green cast, making such gemstones less marketable. Messrs. Borden and Key experimented with some of this inferior London Blue product by bombarding it with electrons, and thus became the first to produce "California Blue" (aka Super Blue, Electra Blue, American Blue). The cost of buying London Blue gemstones from Romanelle was high and the cost of Brazilian rough which would produce intense sky blue colors was still low, so they made limited use of their invention.
During the 1970's and early 1980's a great deal of misleading and incorrect information relating to gemstone irradiation was published in the trade journals. Dr. George Rossman at Caltech, the GIA, and others elsewhere began research in the field in the mid 1970's, but no one was able to actually explain the source of blue colors which formed in topaz.
By 1984 or early 1985, a product similar to, but not necessarily the same as, California Blue was being produced by Zimmerman in Germany and marketed in the USA. Several different qualities of blue color abounded in the trade, all with the appellation "Swiss Blue". Stones from some sources had the appearance of California Blue, but from other sources they merely looked strong in blue with some greyishness.
During the 1984-1985 time frame, I received some dark greyish London Blue stones from a customer of my ongoing gemstone color enhancement service (United Radiant Applications) and was asked to improve the color, which I did by repeating the former experiment of Messrs. Borden & Key, using electron irradiation to produce "California Blue" topaz. Prior to this I had established the use of heat, both to lighten London Blue that was over-irradiated and to eliminate some of the greenish or greyishness in bad batches and had offered heat treatment of London Blue Topaz as a service to my customers. Thus, heating either before or after the application of electron bombardment was naturally used to help the process along. I found that some types of London Blue topaz were very stubborn, having to be heated very much hotter and longer than other types to lighten color or remove undesirable tints. Some required only one hour (approx. 800 MR) of electron bombardment, but others ten hours. (approx. 8000 MR).
I immediately recognized the commercial importance of Borden and Key's experiment, because, unlike theirs, my principal occupation was treating gems for customers. Market conditions had changed so that poorly colored London Blue was inexpensive and heavily discounted relative to the better product. So I began at once to offer to produce "Super Blue", as it was then called, from poorly colored London Blue.
However, approximately two weeks later, Richard Fournier did the same experiment at the irradiation lab I also used. As he had begun in the early 80's to produce large amounts of London Blue, he was able to take much greater immediate commercial advantage of the process with his own material.
The lab that Fournier and I used had recently opened a new linear accelerator facility, and the arrangements for irradiating topaz were changed from those formerly used.